Field of the Disclosure
The disclosure relates to a power gating circuit, and relates particularly to a power gating circuit and a control method for a power gating switch thereof.
Description of Related Art
Along with portable products (for example, a cell phone, a digital camera, a notebook computer and the like) becoming increasingly widespread, how to reduce the power consumption of the portable products has currently become a significantly important task.
One of the methods for reducing the power consumption of a circuit is to use a power gating circuit. The power gating circuit may control the power supply situation of the power supply circuit to the function circuit. When a function circuit enters power saving mode, the power gating circuit may make the power supply circuit stop supplying power to the function circuit, and may resolve the sub-threshold current leakage problem of the function circuit blocks, and lowering the overall power consumption.
FIG. 1 is a circuit diagram of a conventional power gating circuit 100. The power gating circuit 100 in FIG. 1 is implemented by connecting a plurality of inverters INV11, INV22, INV33 and power gate switches SWP11, SWP12 in series. An input signal VS defines a powered period of a function circuit 10. Whether to allow a voltage provided by a voltage source VDD1 to pass through the power gating switch SWP11 to supply power to the function circuit 10 may be determined by controlling an input signal VS. When the function circuit 10 enters power saving mode, the power gating circuit 100 may make the voltage source VDD1 stop supplying power to the function circuit 10. When the power gating switch SWP11 cuts off the transmission path between the voltage source VDD1 and the function circuit 10, and/or when the power gating switch SWP12 cuts off the transmission path between the ground voltage GND and the function circuit 10, the power consumption of the function circuit may be reduced effectively.
However, the power gating switches SWP11, SWP12 require a substantially large path area to transmit large amounts of current to the function circuit 10 when the power gating switches SWP11, SWP12 of the power gating circuit 100 turns on. In order to turn on the power gating switches SWP11, SWP12 which have large path areas, a conventional power gating circuit is required to consume a large current of a high voltage source VPP, referred to as a wake up current. A voltage of the voltage source VPP typically is greater than the voltage of the voltage source VDD1. In order to supply the large amounts of current, a large voltage pump and a capacitor needs to be disposed on the voltage source VPP. Therefore, how to develop a circuit to reduce the large current of the voltage source VPP that is consumed when switching the power gating circuit effectively is a problem which needs to be solved.